plaza hotel has residences (the ones you mentioned) that can be in hotel inventory, and im pretty sure not all of them were sold in bulk to the bulk buyer, so if some are currently owned by individual owners, you could contact them, and or local high end realtors
the bigger residences at plaza are like the 'tower' residences at trump international, which are different from the 'condohotel' units (which can be occupied 365 nights a year by owner) at plaza and trump and the fractionals at st regis
hmm, i actually worked up partial list of (plaza) original sale prices, ill take a look